The present invention relates generally to timing devices, and more specifically to an appliance timer having a sub-interval circuit for providing switching functions during the normal dwell time of the timer.
Appliance timers are commonly used in many household appliances, such as dishwashers, clothes washers, and clothes dryers. The appliance timer controls operation of the appliance by actuating and deactuating switch assemblies which start and stop various work functions within the appliance such as a rinse function in the case of a clothes washer. The switch assemblies within the appliance timer are actuated and deactuated as a result of interaction between a number of cam surfaces defined in a camstack of the appliance timer and a number of cam followers which are respectively associated with the switch assemblies.
Each of the switch assemblies typically includes an upper circuit blade and a lower circuit blade with an intermediate circuit blade positioned therebetween. A first end of each of the upper, lower, and intermediate circuit blades includes a terminal which is electrically coupled to components associated with the appliance.
A second end of each of the upper, lower, and intermediate circuit blades cooperate with the camstack of the appliance timer. Typically, the upper circuit blade and the lower circuit blade are generally passive, whereas the intermediate circuit blade is generally active. In particular, the second end of the lower circuit blade has a blade support molded thereto. A bottom edge of the blade support contacts a portion of the camstack which does not have a varying cam surface defined therein. Therefore, as the camstack rotates, the lower circuit blade is not moved upwardly or downwardly. Moreover, a top edge of the blade support supports the second end of the upper circuit blade. Hence, rotation of the camstack does not cause the upper circuit blade to be moved upwardly or downwardly.
However, the intermediate circuit blade includes a cam follower which cooperates with a cam surface defined in the camstack. When the cam follower encounters a drop defined in the cam surface, the intermediate circuit blade is placed into electrical contact with the lower circuit blade. More specifically, the intermediate circuit blade includes an electrical contact that is urged into contact with a similar electrical contact included in the lower circuit blade when the intermediate circuit blade is dropped onto the lower circuit blade. To subsequently break the electrical contact between the intermediate circuit blade and the lower circuit blade, cam lift is defined in the cam surface which lifts the cam follower of the intermediate circuit blade back to its original position.
In order to place the intermediate circuit blade in electrical contact with the upper circuit blade, a cam lift (as opposed to a drop) is defined in the cam surface of the camstack. As the camstack is rotated, the cam follower of the intermediate circuit blade is advanced up the cam lift of the cam surface thereby placing the intermediate circuit blade into electrical contact with the upper circuit blade. More specifically, the electrical contact of the intermediate circuit blade is urged into contact with a similar electrical contact included in the upper circuit blade. To subsequently break the electrical contact between the intermediate circuit blade and the upper circuit blade, a drop is defined in the cam surface which drops the cam follower of the intermediate circuit blade back to its original position.
A subinterval circuit of a washer or dishwasher timer is used to provide switching for functions such as spray rinse in a washing machine and water fill valves in a dishwasher. Historically, the subinterval circuit has been limited to a single bottom circuit. The circuit is typically put on a bottom blade where it can easily be actuated by a subinterval lever that follows a subinterval cam profile. This profile causes the subinterval lever to open and close a bottom set of contacts by lifting and dropping the intermediate circuit blade of this circuit. When the intermediate blade is lifted by the subinterval lever, the circuit is open, when the intermediate blade is dropped by the sub-interval lever the circuit is closed. The subinterval lever is actuated by a cam profile which is molded as a part of the primary drive cam of the timer. Since the subinterval lever is actuated by the primary drive cam, this make/break action occurs every interval. If it is desired that the circuit not be made during some intervals, it can be masked off by a neutral radius on the main timer camstack. This way, even though the subinterval cam profile allows the subinterval lever to drop, the intermediate blade is still held in the neutral position by the neutral cam profile of the main timer camstack. When it is desired that the circuit be made, the main timer camstack profile is made to have a bottom radius, allowing the intermediate blade to drop and make the bottom circuit when the subinterval lever is actuated by the subinterval cam.
With washing machines becoming more complex and offering more features, it is now desirable to provide a double throw subinterval circuit, where the subinterval cam has three profiles, bottom, neutral, and top. This allows the subinterval lever to actuate the intermediate blade to make and break both a bottom and a top circuit. The bottom circuit is still masked out by the cam profile on the main timer camstack as described above but the top circuit will make every interval per the top radius of the subinterval cam profile. Since it is desirable to have this top circuit not operate every interval, historically it has been turned off electrically through the use of another circuit of the timer. This uses an additional circuit in the timer that could be used to control other machine operations thereby reducing the flexibility of the appliance timer and adding complexity to the timer wiring.
What is needed therefore is an appliance timer that includes a double throw subinterval which allows for the subinterval lever to actuate the intermediate blade to make and break both bottom and top circuits and a mechanical means of masking off the top circuit of a double throw subinterval circuit. This would eliminate the need for a separate electrical circuit to mask off the top circuit of the double throw subinterval switch.